You don't need a motor though, there's a lever thing you put on doors to make them close, they already put them in fridges.
The true reason is that a motor or hinge or even just s thing that makes noise when the fridge is left open too long (mine has that) or whatever doesn't collect your personal data
Everyone's missing the real issue. Springs, motors, or pneumatics don't matter if there's something in the way preventing it from closing. A cheap fridge on an uneven floor will close the door itself if there's nothing in the way, but if the jug of milk is hanging off the edge of the shelf with no room behind it, the door isn't closing without something getting damaged.